Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$7.41	7.161%	$7.9406	$7.94	$7.95	$7.90
Purchase #2	$30.42	9.545%	$33.3236	$33.32	$33.30	$33.30
Purchase #3	$196.46	10.303%	$216.7013	$216.70	$216.70	$216.70
Purchase #4	$93.52	7.531%	$100.563	$100.56	$100.55	$100.60
Purchase #5	$170.31	9.141%	$185.878	$185.88	$185.90	$185.90
Purchase #6	$96.28	5.568%	$101.6409	$101.64	$101.65	$101.60
Purchase #7	$111.87	9.752%	$122.7796	$122.78	$122.80	$122.80
7 purchase totals =	$706.27		$768.8270	$768.82	$768.85	$768.80